The present invention relates to a control apparatus of an automatic transmission mounted on a vehicle, and more particularly to a control apparatus for a multispeed automatic transmission that has five or over five speeds.
In recent years, the number of speeds of automatic transmissions has increased, and also the number of frictional elements such as clutches and brakes has increased with the increase of the number of speeds. Further, a spacing or interval between speed change lines (or shift lines) in a shift map becomes much denser with such increase of the number of speeds. For this reason, speed change easily takes place even according to a small change of operation condition of the vehicle (for instance, a change of throttle opening). Thus, when the interval of shift lines in the shift map becomes denser in this way, so-called two skip shift (for example, shift from 6th speed to 3rd speed) or three skip shift (for example, shift from 6th speed to 2nd speed) tends to occur frequently.
In addition, in the automatic transmission in these days, a gate type speed change lever is installed to enable an easy and positive shift operation for a driver, or a speed change paddle or button are arranged around a steering wheel. Thus, in such automatic transmissions, the two or three skip shift could be performed much frequently by the shift operation of the driver. With respect to such skip shift, especially one skip shift in a downshift direction (for instance, shift from 4th speed to 2nd speed), usually, its programs for optimum speed change control are pre-installed and its data for the control of one skip shift is stored. Then, for example, in the case of one skip downshift as the above shift from 4th speed to 2nd speed, it is performed by and according to the optimum speed change control program.
Further, in a case of the multispeed automatic transmission as well, it could be possible to pre-install the optimum programs for each speed change pattern of the skip shift, such as the two or three skip shift etc. However, in that case, it could lead to an extreme increase of the data amount, which is stored in a control unit for the transmission, and then result in an extreme increase in storage capacity of memory.
Here, in the following, among such skip shifts, a shift for which the speed change control program is not installed is termed “a sequential shift”.
For the above drawbacks, in Japanese Patent Provisional Publication (Tokkaisho) No. 62-46055 (hereinafter is referred to as “JP62-46055”), at the time of the sequential shift, the speed change is sequentially carried out (for instance, in a case of shift from 5th speed to 2nd speed, one skip shift from 5th speed to 3rd speed is first carried out and then shift from 3rd speed to 2nd speed is carried out). On the other hand, in International Publication No. 95/12774 (WO95/12774), upon judging a shift from a higher speed to a lower speed, the shift is carried out through an intermediate speed. And when the shift from the intermediate speed to the lower speed is carried out, this shift is accelerated (or this shift is advanced).